NX How to output incremental drilling code from the post

Can post builder be set up such that drilling operations post out incremental depths, where the retract plane and bottom of the hole depth are values relative to the top of the hole/surface of the part?  This would match the way the print is dimensioned so the operators don't have to do any math to verify the code.

Yes.  As long as the control will correctly interpret the cycle parameters using this syntax, post builder canned cycles includes standard words to handle this situation.  Set the Z word as "cycle feed to negative increment" and the R word to "cycle rapid to distance" to give these levels as increments from the top of the hole plane:

Sample code from a default post drilling a hole in the top of a 40mm tall block, where the MCS is at the bottom corner of the part.  Note the Z depth of the hole finishes at 40mm - 18mm = 22mm deep.  It retracts to a level of 43mm, which is 3mm clearance above the top of the 40mm part.

%

N0010 G40 G17 G90 G71

N0020 G91 G28 Z0.0

N0030 T00 M06

N0040 G00 G90 X25. Y30. S800 M03

N0050 G43 Z50. H00

N0060 G81 X25. Y30. Z18. R43. F250.

N0070 G80

N0080 M02

%

Posting that same operation with a post where the above changes were made to the Z and R words gives this output.  Note that now the Z word has a value of -25mm, which is the relative (incremental) distance from the clear plane at 3mm above the part down to the hole depth of 22mm.  The R word is now the incremental distance of 3mm above the part.

%

N0010 G40 G17 G90 G71

N0020 G91 G28 Z0.0

N0030 T00 M06

N0040 G00 G90 X25. Y30. S800 M03

N0050 G43 Z50. H00

N0060 G81 X25. Y30. Z-25. R3. F250.

N0070 G80

N0080 M02

%